China Ash Yields Salamander Evolution Secrets

John Roach
for National Geographic News
March 27, 2003

A cataclysmic volcanic eruption 160 million years ago was a dark day for thousands of salamanders scurrying about a series of lakes in northern China. The hot ash smothered and buried the amphibians in their tracks.

For scientists who study salamanders, however, that inundation of hot ash was manna from heaven: It allowed for the exquisite preservation of the salamanders, giving scientists a trove of fossils that are revealing the secrets of evolution.

"We have whole bodies, evidence of the soft tissues, numerous individuals, and several species," said Neil Shubin, a biologist at the University of Chicago in Illinois who has been collecting the fossils for three years with his colleague Ke-Qin Gao, a professor of Earth and space science at Beijing's Peking University.

To date the scientists have discovered five new salamander species. They report in the March 27 issue of Nature on a new species that is oldest-known relative to living salamanders.

The fossils of the new species are of tadpole-like larvae and young adults, with soft tissues including eyes, gills, and stomach contents all perfectly preserved. In one of the fossils shown in the paper, the salamander's last dinner is preserved—clam shrimp.

The researchers named the species Chunerpeton tianyiensis. It closely resembles the North American hellbender, a salamander with large, flat head found in the Allegheny Mountains near Pittsburgh, Pennsylvania, that can grow more than 2 feet (61 centimeters) long. It is also similar to the endangered Asian giant salamander, which can grow more than 5 feet (152 centimeters) long.

"This discovery greatly extends the known history of the modern salamander groups, with species specifically recognizable as belonging to two living families," said Robert Carroll, a zoologist at McGill University in Montreal, Canada, who studies the origins and interrelationships of modern amphibians.

The similarities between the Chunerpeton tianyiensis fossils and living salamanders include specific features of the ribs, back, and back of the skull. Parts of the front of the skull and fingers are different, according to Shubin.

Shubin and Gao conducted their fieldwork with funding from the National Geographic Society's Committee for Research and Exploration. Lab analysis of these fossils is supported by a grant from the United States National Science Foundation.

Asian Crucible

Prior to this latest discovery, the oldest known salamander fossils dated back to the Tertiary period, which began 65 million years ago. Despite the 100-million-year gap, however, there are only minor differences between the fossils and their modern equivalents.

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